<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>固定定位</title>
		<style>
			body{
				width: 100%;
				height: 1000px;
				background: url(../table练习/liubang.jpg);
				background-repeat: no-repeat;
				background-size: cover;
			}
			
			#nav{
				width: 100%;
				height: 20px;
				background: black;
				opacity: 0.7;
				/*实现导航栏的固定定位*/
				position:fixed;
			}
		</style>
	</head>
	<body>
		<div id="nav">
			
		</div>
	</body>
</html>
